1. Field of the Invention
The present invention relates to a wrench.
2. Description of the Prior Art
A conventional wrench is subjected to be used through the cooperative engagement of a cam portion disposed at the bottom of a movable jaw and another cam portion disposed at the top of a handle. However, under a required huge torque, such an engagement between the cam portions can easily lead to the collapse of the cam portions and the abrasion of the cam portions after a prolonged use of the cam portions.
In this regard, a wrench disclosed in U.S. Pat. No. 1,434,754 is provided to improve the above problem, in which a spring is disposed in a slot, and rivets are secured to plates and located in the slot. However, since the cooperating projections are located below the slot, and so is the cam shaped projection, the force applied to the movable jaw by the cam shaped projection concentrates mostly at the cooperating projections, the cam shaped projection slantedly and downwardly push the cooperating projections, and only about half the force is used to drive the cooperating projections moving horizontally. In other words, when the wrench which is provided without the use of the engagement of the cam portions is used, it is difficult to operate because only a small part of the force is delivered to the movable jaw and the fixed jaw.
In addition, since the movable jaw and the fixed jaw are secured between two plates, two slots are required, and two rivets are secured to the movable jaw and the fixed jaw and are located in the slot, respectively, to complete the assembly of the wrench. The structure of the wrench is quite complex, thus increasing the manufacturing costs and assembly difficulty.
The present invention is, therefore, arisen to obviate or at least mitigate the above mentioned disadvantages.